In reference to the original, it depends on how I'm feeling and how many themes I've got set up with them ahead of time. I like to have well over 100 photos of each theme depending. Given that with changes in wardrobe and of course breaks, ( I usually have snacks etc for the shoot), I'd say 2-3 hours. Longest was 8 hours with 6 models and 2 photographers taking turns shooting.
Shortest time was 45 minutes for one model and one general theme.
D